 Municipal officials are responsible for providing safe roads for the traveling public. Filling potholes, cutting brush, erecting warning signs, and clearing away ice and snow are some of the things road crews do every day to make roads safe. There is another valuable practice for promoting highway safety, setting speed limits. It is the job of the public official to establish a speed limit, which, as stated in the Uniform Vehicle Code, is reasonable and safe for a given section of roadway. Of course, drivers have to do their part, unless not operate motor vehicles at a speed greater than is reasonable and proper for the prevailing conditions such as snow and ice, fog and darkness. How do you determine what is a reasonable and safe speed? By conducting a traffic engineering survey, the Manual on Uniform Traffic Control Devices and State Law authorize the governing body of a municipality to set speed limits on public highways under its jurisdiction. Sometimes there is a temptation by local officials to set a uniform speed limit for all town roads and let it go at that. Or, they often face considerable pressure by residents to change speed limits. You should not ignore their concerns, of course, but conducting a traffic engineering survey gives you information to face judgments about speed limits on facts and not on guesses or political pressure. A traffic engineering survey allows you to carefully consider the characteristics of each road and its surrounding features. You then have the information you need to make a reasonable judgment in assigning a speed limit that is reasonable and safe. Conducting a traffic engineering survey does not mean you have to be an engineer, but you do have to conduct a survey. There are six factors to consider in conducting a traffic engineering survey. They are road characteristics, the 85 percentile speed or pace speed, roadside development and access, curves and hazardous locations, pedestrian activity and parking practices, and accident history. The first of the criteria is to consider the road itself. Consider such things as the type of surface, the condition of the shoulder, the road's alignment and sight distance, the width of the road and the number of lanes. Determine the maximum grade and the degree of critical curves. Steep roads and sharp curves usually require slower speeds. As you travel the road, look for these and other characteristics and record the information on the form. The second factor is to monitor the speed at which vehicles are traveling. You do this by determining the 85th percentile speed or pace speed. Survey a minimum of 100 vehicles. In fact, surveying exactly 100 vehicles makes it easier to calculate percentages. Determine the speed at or below which 85 percent of the sample of free-flowing vehicles are traveling. This is the 85 percentile speed. The pace speed is similar. It is the 10 mile per hour band of travel speeds containing the largest number of observed vehicles. On low volume roads, instead of gathering a sample of 100 vehicles, you might use several time runs and estimate the speed. A third consideration is to look for roadside development and culture. Is it a densely residential area? A commercial area with many driveways entering the highway. A school zone? A trailer park? Or is it rural farmland? Considering the type and the density of development along the road will help you to determine a reasonable and safe speed for those conditions. The fourth factor is to determine the safe speed for curves or other hazardous locations within the zone such as intersections. You can determine the advisory speed for a curve by driving the section in a conventional automobile. Make several passes along the centerline of the travel lane at constant speeds, increasing the speed by five miles per hour on each pass. Select the speed that allows you to negotiate the curve safely and comfortably without excessive braking or feeling a concern for safety. Determine the maximum safe speed for approaching an intersection based on the stopping site distance. Refer to the handbook for assistance. Use a black-on-yellow advisory speed plate placed below the warning sign to indicate the safe speed. The advisory speed plate cannot be the same or higher than the posted speed limit. A fifth consideration is to record the parking practices and pedestrian activity in the area. Record whether parking is on the roadway or off-street. Is parking controlled by signs or markings or meters? Make a note about pedestrian activities. Higher pedestrian activity may require a lower speed. The sixth and final factor is to record the reported accident experience for a recent 12-month period. High accident experience may indicate a need to moderate the speed limit. On the form, note any other features that may influence traffic movement. With the data you have collected using the six criteria, you will have information to determine a proper speed for the road under consideration. For each road, you are trying to answer the question, what is the reasonable and safe speed for this particular road? A reasonable and safe speed is one that gives a driver time to react and stop or slow down sufficiently to avoid potential conflicts while driving at a comfortable speed. No one of the criteria by itself determines reasonable and safe. To make an informed decision, you must consider all six criteria together. Once you have decided the speed limits for your streets and highways, you must pass a regulation making them official municipal policy. Do this by including them in a speed limit ordinance or traffic ordinance. The ordinance makes the speed limits legal and enforceable. And you have passed the speed limit. It is important to follow all the steps accurately when adopting an ordinance. When people challenge speed limits in court, they may raise questions of authority and whether speed limits were established properly. Refer to the handbook for procedures to adopt an ordinance. Posting signs is the next step. The MUTCD has guidelines for the proper heights, distances and reflectivity for signs to be effective. Do not use speed zones to warn motorists of hazardous conditions. On rural roads, for example, avoid posting speed limits, say from 40 to 30 to 35 to 45 back to 30 and so on. Rather, try to establish one speed limit and use advisory speed plates as needed for curves, hills and other hazardous conditions. Keeping streets and highways safe is a big responsibility. Setting reasonable and safe speed limits based on a traffic engineering survey is an important part of that duty. In addition to this videotape, refer to the handbook Setting Speed Limits. The handbook has several forms, references to statutes, a model ordinance and other useful information. If you have questions about setting speed limits, call Vermont Local Roads or the Vermont Agency of Transportation.